4 replies to this topic

[airwreckarae]

We use both of these devices multiple times a day. They came calibrated from the manufacturer but I've noticed a downward trend in our moisture and water activity. We think it may be time to calibrate or at least test their effectiveness. However, being new to these devices I find the testing methods odd. The water activity meter requires pure NaCl 100g diluted in distilled water and put in a brown bottle for a week prior to doing the actual test. The moisture analyzer requires sodium tartrate dihydrate and the process is daunting. How often do these things REALLY need tested? How often should they be calibrated? Right now we are on a spending freeze and sending it somewhere for the foreseeable is out of the question. Also I just got this job and I have no idea when they were purchased and I've found no documentation on testing or calibration of either. No one can really tell me either. They haven't had a QC Manager in some time. Just a consultant.  

[kingstudruler1]

Its hard to say without the make and model of the instruments to reference and some other relevant info.  

 

 

In general: 

I would buy water activity standards  such as:  40746 - Verification Standards, 6.00 mol/kg NaCl (0.76 aw) Box of 50 Tubes (metergroup.com)

 

Im not sure what is difficult about the sodium tartrate dihydrate.   You just run it as you would a sample on most instruments.   then check the balance portion with a certified weight.   

 

 

the frequency depends on use and MFG recommendations.   probably weekly for both.   If they are for food safety -maybe daily - as everything back to the last good check or calibration is in question.   

 

have the MFG calibrate them once per year or when outside of tolerance.  

[G M]

Its hard to say without the make and model of the instruments to reference and some other relevant info.  

 

 

In general: 

I would buy water activity standards  such as:  40746 - Verification Standards, 6.00 mol/kg NaCl (0.76 aw) Box of 50 Tubes (metergroup.com)

 

...

have the MFG calibrate them once per year or when outside of tolerance.  

 

It depends on the model and style of instrument as stated above.

 

We're using water activity as one of the limits for safety in our HACCP plan, so those have an instrument self-calibration performed at the beginning of each shift (2/d) with purchased standards linked above, and the instrument is sent off for maintenance and calibration each year to the manufacturer.

 

Most of our instruments follow a similar cycle, a verification or automated calibration at least once a day, and a full maintenance and calibration once a year by some certified/licensed body or the manufacturer.

[Alexis M]

Hello there.. Not sure if this will help or not but we are a coffee manufacturing facility... Our Moisture Analyzer is a MCT 600 NIR which is sent out and calibrated annually in addition to in house calibrations that are performed on a weekly basis. 

[Rhewitt33]

Hi. Where I worked previously, we used both. We ran 24/7, so they were used alot. When I noticed the results seemed off, I cleaned them. The amount of GUNK inside was enough to make you lose your lunch. So, moving forward, they both were cleaned weekly. I can't remember which brand they were, but we were able to purchase cleaning kits for both. They may be dirty.